At least two different monomers can be polymerized in the same polymerization system so as to generate a copolymer having those different monomer units arranged as repeating units in one polymer chain, and the copolymer thus obtained can be classified into a random copolymer, an alternate copolymer, a block copolymer, or a graft copolymer, depending on the arrangement of the monomer units. However, no report has been made on the arrangement of monomer units in polymerization reaction of a conjugated diene compound and a non-conjugated olefin.
For example, JP 2000-154210 A (PTL 1) discloses such a catalyst for polymerizing a conjugated diene that contains a transition metal compound of group IV of the periodic table having a cyclopentadiene ring structure, and also discloses α-olefins such as ethylene as monomers which can be copolymerized with the conjugated diene. PTL 1, however, does not at all refer to the arrangement of the monomer units in a copolymer. Further, JP 2006-249442 A (PTL 2) discloses a copolymer of an α-olefin and a conjugated diene compound, but no reference is made on the arrangement of monomer units in the copolymer. Further, JP 2006-503141 A (PTL 3) discloses an ethylene-butadiene copolymer synthesized by using a catalytic system consisting of a specific organometallic complex, but merely describes that the butadiene as a monomer is inserted in the form of trans-1,2-cyclohexane into the copolymer, without making any reference to the arrangement of monomer units in the copolymer.
In addition, there is no description or suggestion in PTL 1 to 3 that a rubber having excellent rollability and wear resistance can be manufactured by using a random copolymer which contains, by more than 30 mol %, a unit derived from a conjugated diene compound in the copolymer.
Further, JP 11-228743 A (PTL 4) discloses an unsaturated elastomer composition composed of an unsaturated olefin-based copolymer and a rubber, but merely describes that monomer units in the copolymer are randomly arranged. PTL 4 fails to provide a rubber that has excellent rollability and wear resistance (index).
There is no description or suggestion that a rubber having excellent rollability and wear resistance can be manufactured by using a copolymer which contains, by more than 30 mol %, a unit derived from a conjugated diene compound in the copolymer.